Group 36 - Ryobi Contractor's Saw
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==Introduction== | ==Introduction== | ||
| − | This | + | The Skil saw is a circular saw design for cutting wood or other materials. This hand-held saw is powered by electricity that is converted to mechanical power. The device features 2.3 HP with 4,600 RPM and with the 7 1/4 " 40 tooth blade it weights 13.9 lb. This Skil saw is mainly black and the guards are in gray color. The device contains some of the essentials such as the safety switch and a vent to prevent from disfunctioning. |
==Before Disassembly Section== | ==Before Disassembly Section== | ||
Revision as of 17:14, 3 December 2007
Contents |
Executive Summary
In this project, our group was tasked to disassemble, analyze, reassemble, and recommend our improvements for the Skilsaw Contractor’s Saw. Before we disassembled the saw, we knew that the saw changed AC power into mechanical energy but we weren’t sure exactly how. After we took it apart, we saw that the AC power is transfer through the brushes into the rotor which rotates caused by the magnetic field of the stator. As the rotor spins, it turns gears which rotate the blade at approximately 700 rpm after the 6:1 gear reduction for safety reasons. The disassembly and reassembly both took about an hour and was fairly simple with the exception of a few parts that needed extra care and effort to remove. The saw’s handle and housing for the motor were made of plastics; the upper and lower guards were made of aluminum; and the rest of the saw was made of steel and other metals.
Introduction
The Skil saw is a circular saw design for cutting wood or other materials. This hand-held saw is powered by electricity that is converted to mechanical power. The device features 2.3 HP with 4,600 RPM and with the 7 1/4 " 40 tooth blade it weights 13.9 lb. This Skil saw is mainly black and the guards are in gray color. The device contains some of the essentials such as the safety switch and a vent to prevent from disfunctioning.
Before Disassembly Section
This circular saw is primarily used for cutting wood. It runs on an AC current, and contains a 2.3 hp motor at 4600 rpm, turning electrical energy into mechanical energy. At the beginning of the project, it was new, so the group assumed that its initial operation was correct. The saw is operated by engaging a safety switch, and then a power switch. It was very loud, and even without the torque of the blade, kicked back when it was initially operated. This demonstrated the physical power of the motor. The group estimated that the saw would contain about 40 components, and predicted that those components would be made of plastic, steel, aluminum and copper.
Disassembly Procedure
1. Took out Wrench with hands
2. Remove rubber stopper with T-30 torx bit
3. Remove lower guard lift with T-20 torx bit
4. Remove spring from lower guard with needle nose pliers
5. Removed blade-holding bolt and “washers” with 13mm socket
6. Removed spring ring with swiss army knife
7. Removed C-clip and depth adjustment lever with pliers and a 12mm wrench
8. Removed lower guard with hands
9. Removed 3 short screws with T-20 screw driver and bearing flange
10.Removed pinion shaft
11.Removed 4 long screws from upper gaurd with a T-20 torx screwdriver
12.Removed upper guard with hands
13.Removed armature with hands
14.Removed plain washer and 2 washers from the armature
15.Removed 6 screws to take handle apart with T-20 torx screwdriver
16.Pulled the handle off with hands
17.Removed 2 medium screws and pulled off housing cover with hands
18.Slid out motor brushes with needle nose pliers
19.Took apart brushes with hands
20.Removed 2 long screws from stator
The disassembly was relatively easy except for pulling off the C-Clip, which needed to be slowly worked out of its former position.
After Disassembly
Component List
| Part # | Component Name | Number of Parts of This Type | Material(s) | Manufacturing Process | Image |
|---|---|---|---|---|---|
| 1 | Motor Housing | 1 | Plastic, Brass, Galvanized Steel | Injection Molded, Die Cast and Machined, Stamped |  |
| 2 | Stator | 1 | Plastic, Copper, Magnetic Alloy | Injection Molded, Extruded, Stamped and Soldered |  |
| 3 | Trigger and Safety Switch | 1 | Plastic, Aluminum | Injection Molded, Extruded and Machined |  |
| 4 | Power Cord | 1 | Copper, Plastic | Both Extruded |  |
| 5 | Upper Guard | 1 | Aluminum, Brass | Die Cast and Machined, Machined |  |
| 6 | Pinion Shaft | 1 | Steel | Extruded and Machined. Also dipped in an anti-corrosion coating. |  |
| 7 | Central Washer | 2 | Steel | Die Cast |  |
| 8 | Depth Adjustment Lever | 1 | Plastic | Injection Molded |  |
| 9 | Rubber Stopper | 1 | Rubber | Injection Molded and Vulcanized |  |
| 10 | Handle | 2 | Plastic | Injection Molded |  |
| 11 | Rotor | 1 | Steel, Copper, Plastic | Stamped, Extruded and Machined, Extruded, and Injection Molded |  |
| 12 | Vent Cover | 1 | Plastic | Injection Molded |  |
| 13 | Lower Guard | 1 | Aluminum | Die Cast |  |
| 14 | Carbon Brush | 2 | Plastic, Copper, Carbon, Brass | Injection Molded, Extruded, Machined, Stamped |  |
| 15 | Lower Guard Lift Lever | 1 | Plastic | Injection Molded |  |
| 16 | Long Screw | 6 | Steel | Extruded and Machined |  |
| 17 | Medium Screws | 8 | Steel | Extruded and Machined |  |
| 18 | Short Screws | 4 | Steel | Extruded and Machined |  |
| 19 | Central Bolt | 1 | Steel | Extruded and Machined |  |
| 20 | Long Spring | 1 | Steel | Extruded |  |
| 21 | O-Spring | 1 | Steel | Extruded |  |
| 21 | C-Clip | 1 | Steel | Stamped |  |
| 22 | Large Gauge Screw | 1 | Steel | Extruded and Machined | |
| 23 | Wing Nut Bolt | 1 | Steel | Extruded and Machined |  |
| 24 | Wing Nut | 1 | Steel | Stamped |  |
| 25 | Wrench | 1 | Galvanized Steel | Stamped |  |
| 26 | Plain Washer | 1 | Aluminum | Stamped |  |
| 27 | Washer | 1 | Aluminum | Stamped |  |
| 28 | Bearing Flange | 1 | Steel | Machined |  |
| 29 | Depth Adjustment Nut | 1 | Steel | Machined |  |
Design Changes
While the long, medium, and short screws all took the same size bit and had the same thread, the large screw took a different bit. This group suggests that the large screw be changed to accommodate the same size bit as the others.
Also, the carbon brushes are simply set into the saw and held in place by the vent. The group suggests that the brushes are fastened in place independently.
PUT CAD IN HERE!!!
Assembly
- Document each step to reassemble the product
- How difficult was each assembly step?
- What types of tools were required to perform this step?
After Assembly
Reassembly
Upon reassembling the saw, the group successfully tested it. It ran almost exactly as it had before, but once the switch was disengaged, the motor continued to spin from its momentum. The group surmised that the broken copper wiring in the carbon brushes must have had something to do with the braking of the motor. This problem could be quite dangerous if the lower guard malfunctioned.
Design Problems/ Changes
The group discovered that there was a lot of plastic used in the saw's construction. We felt that there was not enough metal at pivotal load-bearing locations on the saw. Instead, we found plastic at these locations. The high power of the drill and the brittle nature of the plastic could lead to a dangerous malfunction, were some of the plastic supports to break. We suggest that high-load areas be reinforced with some sort of steel.
We also noticed that there were no ball bearings on the bushings. Instead, the bushings were heavily lubricated with grease. If the lubricant was burned away by regular use, there could be a large amount of friction created, efficiently "burning out" the motor. We suggest that to increase the longevity of the saw, ball bearings are added to the bushings.
References
Product Detail - 7 1/4" Skilsaw - Model #5400-01. (n.d.). Retrieved December 3, 2007, from http://www.skiltools.com/en/AllTools/Category/Product/default.htm?pid=5400-01&cid=192160
